We have prepared four tryptophan mutants of adenylate kinase from Ecofi (S41 W, F86W, Y133W,F137W). The fluorescence properties of these mutants are very diverse indicating a wide range of localized conformational variability for the tryptophan reporter groups. For example, the F86W and S41W, respectively, the emission maximum range from 325 to 357 nm and the lifetime from 3 to 7 ns.